The present invention relates to the isomerization of an alkylation product, formed by the alkylation of phenol with an olefin in the presence of a super acid catalyst containing Bronsted acid functionality. The term xe2x80x9cisomerization, as used herein, is meant to indicate the change in overall isomer distribution of an alkylated phenol composition by intra- and/or intermolecular mechanism(s). Such a product normally contains a certain level of undesired mono, di and tri-substituted ortho-alkylphenols (or mixture thereof). It is desired to reduce the level of such ortho-substituted alkylphenols, in such an alkylation product since such ortho-substituted components are significantly less reactive in any later desired phosphorylation reaction using the alkylated phenol and also may be deemed by some persons to be more undesired from a toxicological viewpoint. The phosphorylation of such materials is a well-known reaction and involves treating them with a phosphorylating reagent (such as phosphorus oxytrichloride) at moderately elevated temperature (such as about 100xc2x0 C. to about 200xc2x0 C.), preferably in the presence of a Friedel-Crafts catalyst.
One prior art reference that relates to the use of trifluoromethane sulfonic acid (also termed xe2x80x9ctrifle acidxe2x80x9d) as the catalyst to achieve the general type of isomerization that forms the subject matter of the present invention is U.S. Pat. No. 4,103,096 to S. L. Giolito et al., which is incorporated herein in its entirety. This patent illustrates, in general terms, one conventional way in which this isomerization reaction has been practiced.
While the use of trifluoromethane sulfonic acid catalyst, as just described, has been utilized commercially, its use is attendant with certain disadvantages. The use of relatively high levels of this catalyst (e.g., 800 to 1000 ppm) may be needed for the desired level of isomerization to take place, and the use of such levels of this acid can cause unacceptable color change in the product of the reaction. Trifluoromethane sulfonic acid is a strong acid that can cause corrosion damage in the process equipment that is used. This catalyst cannot be recovered and hence the catalyst costs are not trivial. Finally, the isomerization reaction using this acid is rather slow (e.g., 40 to 60 hours) in order to reach the target isomer distribution.
Other methods which have been proposed for practicing analogous isomerization reactions are shown in the following patent and literature references: Japanese Patent Publication No. 45-30091/1970; U.S. Pat. No. 3,014,079; and J. Org. Chem., 38, 1929 (1973).
The present invention relates to the isomerization of the previously described alkylation product to reduce the level of ortho-substituted product therein using a new class of catalyst: a solid acid catalyst.